How does a throttle cause a decrease in pressure?

In summary, a throttle does not directly cause a decrease in pressure. Rather, it allows fluid to flow from a high pressure region to a low pressure region, where it expands at constant enthalpy. The pressure difference is set by conditions on each side of the throttle, such as the size of the reservoir or the flow into it.
  • #1
tomz
35
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I am a new starter on thermodynamics, here is my question.How does a throttle work?
I can understand the equation behind throttling process, how enthalpy is conserved...etc
But I cannot understand how throttle actually achieve the decrease in pressure? is it through turbulent the flow?

Thanks in advance
 
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  • #3
It isn't the throttle that causes the pressure decrease. The fluid flows from a region of high pressure to a region of low pressure and there expands at constant enthalpy, according to Bernoulli's equation.

Yes, a throttle has a high pressure side and a low pressure side and fluid passes from one to the other through the throttle, but the pressure is set by conditions on each side.

So for instance the high pressure side might be a container of fluid at high pressure that is expanded into a large chamber at lower pressure or even the atmosphere, which maintains the low pressure.
The high pressure may be maintained by the size of the reservoir, or by flow into the reservoir.
 

1. What is throttling in thermodynamics?

Throttling in thermodynamics refers to a process where a fluid is allowed to flow through a small opening or valve, causing it to undergo a rapid expansion or compression. This results in a decrease in the fluid's temperature and pressure, leading to changes in its thermodynamic properties.

2. What is the purpose of throttling in thermodynamics?

The main purpose of throttling in thermodynamics is to control the temperature and pressure of a fluid. It is often used in refrigeration and air conditioning systems to decrease the temperature of a gas or liquid, and in steam turbines to increase the pressure of steam.

3. How does throttling affect the enthalpy of a fluid?

Throttling causes a decrease in the enthalpy of a fluid, as the rapid expansion or compression leads to a decrease in the fluid's internal energy. This decrease in enthalpy is responsible for the cooling effect observed in throttling processes.

4. What are the assumptions made in the throttling process?

The main assumptions made in the throttling process are that the fluid is in a steady state, there is no heat transfer or work done during the process, and there are no significant changes in kinetic and potential energy. These assumptions allow for simplified calculations and analysis of the process.

5. What are some practical applications of throttling in thermodynamics?

Throttling is commonly used in refrigeration, air conditioning, and steam turbine systems. It is also used in control valves to regulate the flow of fluids in industrial processes. Additionally, throttling can be used in gas pipelines to control the pressure and flow of natural gas or other gases.

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